1. Field of the Invention
The present invention relates to an automatic balancing apparatus that balances the rotation of an object, a rotating apparatus on which the automatic balancing apparatus is mounted, a disc drive apparatus, and a balancer that is mounted in an automatic balancing apparatus.
2. Description of the Related Art
When a disc such as a record medium is rotated on a turn table of a disc drive apparatus such as an optical disc drive apparatus or a magnetic disc drive apparatus that records and/or reproduces for example data, the rotation of the disc may be unbalanced. As a result, the stability of recording/reproducing may decrease.
A technology of improving the balance of the rotation of a disc has been proposed for example in Japanese Patent Application Laid-Open No. Hei4-312244, paragraph (0006), FIG. 1. In this related art reference, a disc-shaped member having a space portion that accommodates magnetic fluid as a balancer is disposed so that it is rotated together with a motor shaft. The disc-shaped member has a boss portion. A ring magnet is mounted on a side circumferential surface of the boss portion. Thus, when the rotation rate of the rotation shaft is low, the magnetic fluid is attracted by the ring magnet so that the disc-shaped member is not unbalanced.